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Spring Migration
During spring, adult eagles return to breeding grounds when weather and food permit, usually January–March. They move north rather rapidly even though conditions at their breeding grounds are not yet ideal because their biological clocks are telling them breeding time is near. The hormonal drive to initiate nest building and courtship outweigh the possible difficulties in finding food during this time.
Migrating eagles fly during the day at speeds averaging 30 miles per hour. To help them soar, eagles use thermals, which are rising currents of warm air and up-drafts generated by terrain, such as valley edges or mountain slopes. Soaring is achieved with very little wing-flapping, enabling them to conserve energy. Long-distance flights are accomplished by climbing high in a thermal and then gliding downward to catch the next thermal, where the process is repeated.
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